A particularly prevalent form of cardiovascular disease is atherosclerosis which creates a restriction or blockage of the blood flow in the cardiovascular system leading to the heart. Vascular complications produced by atherosclerosis, such as stenosis, aneurysm, rupture or occlusion, in which the atherosclerosis is advanced and the health of a patient is jeopardized, call for surgical intervention. In many cases, a blockage or restriction of the blood flow leading to the heart can be treated by a coronary artery bypass graft (CABG) procedure.
In a CABG procedure, the obstruction is bypassed by a vascular conduit established between an arterial blood source and the coronary artery to be bypassed at a location beyond the obstruction. The vascular conduit is typically a non-critical artery or vein harvested from elsewhere in the body. Often, the saphenous vein, harvested from the patient's leg, is used as the vascular conduit wherein one end of the vein is anastomosed to the aorta and the other end is anastomosed to the diseased coronary artery at a location distal to the obstruction. This procedure is known as a "free bypass graft." Alternatively, an "in situ bypass graft" procedure may be employed, wherein an artery proximate the heart is used as the bypass conduit. In an in situ bypass graft procedure, the surgeon dissects a sufficient length of the artery from its connective tissue, then transects the artery, and connects the transected end to the diseased coronary artery distal to the obstruction while leaving the other end attached to the arterial supply, thus restoring blood flow to the heart. Recent studies have shown that it is preferable to use a pedicled or transected arterial conduit, rather than a harvested vein, as they tend to have a better patency rate than free bypass grafts. Two other obvious advantages of in situ bypass grafts over free bypass grafts is that they require only one anastomotic connection rather than two, and they are accessible through the thoracic cavity, obviating the need for incisions elsewhere in the body.
The internal mammary arteries (IMAs), left (LIMA) and right (RIMA), are particularly desirable for use as in situ bypass grafts as they are conveniently located, have diameters and blood flow volumes that are comparable to those of coronary arteries, and typically have superior patency rates. Extending from the subclavian arteries near the neck to the diaphragm and running along the backside of the ribs adjacent the sternum, the IMAs deliver blood to the musculature of the chest wall. The LIMA is suitable as an arterial source for target locations on the left anterior descending coronary artery (LAD), the diagonal coronary artery (Dx), the circumflex artery (Cx), the obtuse marginal artery, and the ramus intermedius coronary artery. The RIMA is available for connection to all of the same target locations, as well as the right coronary artery and the posterior descending artery.
Use of either IMA as a bypass graft first involves harvesting the IMA free from the chest wall. In conventional CABG approaches, access to the IMA is obtained through a sternotomy or major thoracotomy. Typically an electrosurgical tool (often called a "Bovie") is used to free a length of the IMA by incising the endothoracic fascia to free the IMA. The use of such electrosurgical devices is well known in the art and can be crucial in controlling bleeding during harvesting of the IMA. Such devices are typically in the form of scalpels, forceps, and scissors, and employ at least one conductive electrode connected thereto. Radio frequency (RF) energy is conducted through this electrode to either a remote return electrode in the form of a body plate (monopolar technology) or to a second, closely-spaced conductive electrode (bipolar technology). Current passing through the gap between the two electrodes coagulates blood while separating tissue placed between the two electrodes. Because radio frequency (RF) energy is passed through the patient's body in monopolar electrosurgery, there is a greater potential for unintended injury to body tissues as the electrical current passes through them to the return electrode. Bipolar electrosurgical devices provide an improved margin of patient safety as both the active and return electrodes are located on the surgical instrument itself, not requiring the RF energy to travel through unrelated tissue. An example of a bipolar scalpel is disclosed in U.S. Pat. No. 5,013,312.
Utilizing an electrosurgical device such as the bipolar instruments described above, a surgeon cuts away or dissects a section of the IMA, usually about 10 to 20 cm in length, from the surrounding fascia with the target vessel still intact. As the IMA is freed from the fascia, the side branches of the IMA are then cut or cauterized. A section of the IMA is chosen which, when cut distally, will reach the desired anastomosis site on the diseased coronary artery to be bypassed, typically the LAD. A removable clamp is then applied to the IMA near the distal end of the mobilized section but proximal to the point at which the vessel is to be transected. The clamp temporarily occludes the IMA and is later removed to reestablish blood flow once the anastomotic connection has been made. One or more surgical clips are then applied to the IMA distal to the point at which it is to be transected. After the clips are applied, scissors or other cutting devices are then used to transect the IMA near the distal end of the mobilized section between the removable clamp and the surgical clips, creating a free end. The "pedicled graft" is then attached to the targeted diseased coronary artery while the proximal portion of the IMA remains attached to the subclavian artery. Once the anastomosis is complete, blood flow is initiated through the graft vessel by removing the clamp from the IMA.
With conventional CABG, harvesting of the IMAs is accomplished with relative ease due to the working space made available by stemotomy or major thoracotomy. Recently, progress has been made in advancing minimally invasive surgical techniques, particularly in cardiothoracic surgery, which eliminate the need for a sternotomy or major thoracotomy. Access to the heart with these minimally invasive techniques is obtained through one very small surgical incision or through several percutaneous cannulas known as trocar sleeves positioned intercostally in the thoracic cavity of the patient. Visualization of the operative area may be facilitated by thoracoscopes which typically consist of a video camera configured for introduction through a small incision or trocar sleeve to allow observation of the target area on a video monitor.
With the advent of these minimally invasive techniques, harvesting the IMA has become more complex and difficult due to restricted work space and access, and to reduced visualization of the IMA. This is a concern as a high degree of precision is required when harvesting a bypass vessel to avoid injury (such as over cutting or cauterizing) to the vessel which may in turn lead to increased rates of occlusion in the vessel in the months and years after the procedure.
Although many low-profile surgical instruments, and particularly electrosurgical devices, such as bipolar forceps and scissors for cauterizing and/or cutting tissue and vessels, have been developed to aid in minimally invasive surgery on organs and ducts of the abdominal and pelvic cavities, such has not been the case for harvesting the IMA and other similarly situated arteries in minimally invasive CABG procedures. Surgical instruments designed for laparoscopic and other minimally invasive applications are not generally suitable for performing minimally invasive CABG. Most laparoscopic procedures, for example, target body structures which are quite large in comparison to coronary vessels, and do not require the high degree of precision required in a CABG procedure. Accordingly, laparoscopic instruments generally have lengths which are too short, are very straight, and provide only limited angular orientation, making them unsuitable for harvesting of the IMA through a minimal thoracotomy or an intercostal puncture site. Furthermore, such laparoscopic instruments have relatively large end-effectors (e.g., blades) with relatively large ranges of movement, making such instruments ill-suited for use in IMA harvesting in minimally invasive CABG procedures. In addition, such instruments commonly have finger loops or pistol-type actuators gripped in the user's palm or between the user's thumb and forefinger, such as the bipolar scissors and forceps disclosed in U.S. Pat. Nos. 5,540,685 and 5,445,638, respectively, limiting the sensitivity and precision with which such instruments can be manipulated and actuated. Such finger loops or pistol-type grips also are limited to a single orientation in the user's hand and cannot be repositioned in the hand to allow better access to a body structure or to change the orientation of the end-effector.
It is therefore an object of the present invention to provide an improved electrosurgical device for the hemostatic harvesting of arteries to be used for minimally invasive CABG procedures.
Another object of the present invention is to provide an electrosurgical device having a suitable profile, length, and angular orientation for introduction through a small incision or surgical puncture and for reaching the LIMA, RIMA or similarly situated artery.
Another object of the present invention is to provide an electrosurgical instrument having end-effectors which have very small dimensions and are capable of very subtle ranges of motion.
Still another object of the present invention is to provide an electrosurgical instrument that provides ergonomic, comfortable, and sensitive actuation by one finger.
Another object of the present invention is to provide an electrosurgical instrument which allows for multiple orientations in a user's hand.
It is also an object of the present invention to provide a method of harvesting a vessel which provides for cutting and/or cauterizing of tissue by means of a finger activated actuator.